This invention relates to an aerial work platform apparatus with an anti-tipping supplement, more particularly to mobile elevating work platform apparatus comprising a scissors-type lift on a vehicle for lifting and lowering a work platform with a supplemental (complementary) system for stabilizing the apparatus when the work platform is lifted to inhibit the tipping over of the apparatus, especially in a situation where the vehicle encounters uneven going, such as when a wheel of the vehicle goes down in a pothole or up on a bump causing the apparatus to tilt.
The invention is generally in the field of apparatus such as disclosed in U.S. Pat. No. 5,890,737 dated Apr. 6, 1999 entitled xe2x80x9cPothole Protection Mechanism for a Lifting Devicexe2x80x9d, to which reference may be made for a discussion of the tip-over problem encountered by mobile elevating work platform lifts, particularly those comprising a scissors-type lift on a wheeled vehicle. The invention may be regarded as involving an improvement thereover and, more to the point, may be regarded as an improvement on a prior apparatus sold by the assignee of this application having a bar which is reciprocal generally horizontally on the vehicle in forward and rearward direction relative to the vehicle in response to lifting and lowering of the work platform for rotating forward and rearward horizontally extending shafts linked to stabilizers on opposite sides of the vehicle for lowering the stabilizers from a raised retracted position to a lowered stabilizing position on the lifting of the platform and raising the stabilizers to retracted position on the lowering of the platform.
Among the several objects of the invention may be noted the provision of aerial work platform apparatus with an improved anti-tipping system; the provision of such apparatus in which the anti-tipping system has a reduced total of parts and a reduced quantity of different parts; the provision of such apparatus in which the anti-tipping system is most effectively self-locking; and the provision of such apparatus in which the anti-tipping system is of relatively economical construction as to both components and fabrication.
In general, aerial work platform apparatus of this invention comprises a vehicle, a work platform, a lift on the vehicle for elevating and lowering the work platform, and a stabilizer for inhibiting tipping over of the apparatus when the work platform is elevated. The stabilizer is mounted on the vehicle for movement between a raised retracted position and a lowered position for engagement with the surface traversed by the vehicle should the apparatus start tipping. A drawbar is mounted on the vehicle for generally vertical reciprocation movable up on rise of the lift and down in response to lowering of the lift, and mechanism operable by the drawbar has a connection with the stabilizer for moving the stabilizer up to its raised retracted position on lowering the lift with accompanying downward movement of the drawbar and down to its lowered position on rise of the lift with accompanying upward movement of the drawbar.
In one embodiment, two stabilizers are provided for inhibiting tipping over of the apparatus when the work platform is raised. Each stabilizer extends longitudinally of the vehicle, one at one side and the other at the other side of the vehicle, and each comprises a bar mounted on the vehicle for movement between a raised retracted position and a lowered position for engagement with the surface traversed by the vehicle. A drawbar is mounted on the vehicle for generally vertical reciprocation movable up on rise of the lift and down in response to lowering of the lift. Two drawbar-operated stabilizer operating mechanisms are provided, one for the one stabilizer and the other for the other stabilizer. Each such mechanism is operable by the drawbar and has a connection with the respective stabilizer for moving the respective stabilizer up to its raised retracted position on lowering the lift with accompanying downward movement of the drawbar and down to its lowered position on rise of the lift with accompanying upward movement of the drawbar.
In a preferred embodiment, the aerial work platform apparatus comprises a vehicle, a work platform, and a scissors lift on the vehicle for elevating and lowering the work platform. Two stabilizers are provided for inhibiting tipping over of the apparatus when the scissors lift is raised to elevate the work platform. Each stabilizer extends longitudinally of the vehicle, one at one side and the other at the other side of the vehicle, and each comprises a bar having arms thereon pivoted on the vehicle for swinging movement on a generally horizontal axis extending longitudinally of the vehicle between a raised retracted position wherein the arms extend inward from the respective side and a lowered position extending downward for engagement with the surface traversed by the vehicle. A double-sided rack is mounted on the vehicle for generally vertical reciprocation between a lowered retracted position and a raised position movable up to its raised position on rise of the scissors lift and down to its retracted position in response to lowering of the lift. Two pinions, one on each side of the rack, each having a crank pin thereon, are mounted on the vehicle for rotation by the rack on a horizontal axis between a retracted position and an advanced position of the crank pin. Two links extend transversely of the vehicle, each interconnecting a respective crank pin and a respective stabilizer arm for swinging of the stabilizer bars to their lowered position on upward movement of the rack in response to rise of the lift and to their retracted position on downward movement of the rack on lowering of the lift.
In another aspect of this invention, the aerial work platform apparatus includes a vehicle, a work platform on the vehicle, and a lift on the vehicle for raising and lowering the work platform. The apparatus also includes a stabilizer extending lengthwise of the vehicle when the work platform is elevated, mounted on the vehicle for movement between a raised retracted position and a lowered position for engagement with the surface traversed by the vehicle should the apparatus start tipping. Mechanism is provided for moving the stabilizer up to its raised retracted position on lowering the lift and down to its lowered position on rise of the lift. This mechanism comprises, in one embodiment, a crank mounted on the vehicle for rotation on an axis extending lengthwise of the vehicle between a retracted angular position and an advanced angular position, the crank being rotatable from the retracted to the advanced position on rise of the lift and from the advanced position to the retracted position on lowering of the lift. The mechanism also includes a link extending transversely of the vehicle interconnecting the crank and stabilizer for moving the stabilizer up to its raised retracted position on the rotation of the crank on lowering the lift and down to its lowered position on the reverse rotation of the crank on rise of the lift.
Other objects and features will be in part apparent and in part pointed out hereinafter.